This invention relates generally to medical systems and procedures and more particularly to systems and procedures for delivering a flowable treatment agent into targeted tissues, e.g., cardiac tissue, of a living being.
Cardiovascular disease is the leading cause of death in the industrial world today. During the disease process, atherosclerotic plaques develop at various locations within the arterial system of those affected. These plaques restrict the flow of blood through the affected vessels. Of particular concern is when these plaques develop within the blood vessels that feed the muscles and other tissues of the heart. In healthy hearts, cardiac blood perfusion results from the two coronary arterial vessels, the left and right coronary arteries that perfuse the myocardium from the epicardial surface inward towards the endocardium. The blood flows through the capillary system into the coronary veins and into the right atrium via the coronary sinus. When atherosclerosis occurs within the arteries of the heart it leads to myocardial infarctions, or heart attacks, and ischemia due to reduced blood flow to the heart tissues. Over the past few years numerous devices and methods have been evaluated for treating cardiovascular disease, and for treating the resulting detrimental effects that the disease has upon the myocardium and the other heart tissues. They are: traditional surgical methods (e.g. open heart surgery), minimally invasive surgery, traditional interventional cardiology (e.g. angioplasty, atherectomy, stents), and advanced interventional cardiology (e.g. catheter based drug delivery). Other recent advances in cardiovascular disease treatment involve transmyocardial revascularization (TMR), and growth factor and gene delivery.
Traditional methods for treating cardiovascular disease utilize open surgical procedures to access the heart and bypass blockages in the coronary blood vessels. These procedures require an incision in the skin extending from the supra-sternal notch to the zyphoid process, the sawing of the sternum longitudinally in half, and the spreading of the rib-cage to surgically expose the patient's heart. Based upon the degree of coronary artery disease, a single, double, triple, or even greater number of vessels are bypassed. Each bypass is typically performed by creating a separate conduit from the aorta to a stenosed coronary artery at a location distal to the occluded site. In general, the conduits are either synthetic or natural bypass grafts. Grafting with the internal thoracic (internal mammary) artery directly to the blocked coronary site has been particularly successful with superior long-term patency results. During conventional cardiac surgery, the heart is stopped using cardioplegia solutions and the patient is put on cardiopulmonary bypass. The bypass procedure uses a heart-lung machine to maintain circulation throughout the body during the surgical procedure. A state of hypothermia may be induced in the heart tissue during the bypass procedure to preserve the tissue from necrosis. Once the procedure is complete, the heart is resuscitated and the patient is removed from bypass.
There are great risks associated with these traditional surgical procedures such as significant pain, extended rehabilitation time and high risk of mortality for the patient. The procedure is time-consuming and costly to perform. Traditional cardiac surgery also requires that the patient have both adequate lung and kidney function in order to tolerate the circulatory bypass associated with the procedure and a number of patients which are medically unstable are thus not a candidate for bypass surgery. As a result, over the past few years, minimally invasive techniques for performing bypass surgery have been developed and in some instances the need for cardiopulmonary bypass and extended recovery times are avoided. A number of companies, e.g., Heartport, Inc. of Redwood City, Calif. and Cardiothoracic Systems, Inc. of Cupertino, Calif., have developed devices that allow for cardiac surgical procedures that do not require a grossly invasive median sternotomy or traditional cardiopulmonary bypass equipment. The procedures result in a significant reduction in pain and rehabilitation time.
In addition, as an alternative to surgical methods, traditional interventional cardiology methods (e.g. angioplasty, atherectomy, and stents) non-surgical procedures, such as percutaneous transluminal coronary angioplasty (PTCA), rotational atherectomy, and stenting have been successfully used to treat this disease in a less invasive non-surgical fashion. In balloon angioplasty a long, thin catheter having a tiny inflatable balloon at its distal end is threaded through the cardiovascular system until the balloon is located at the location of the narrowed blood vessel. The balloon is then inflated to separate and expand the obstructing plaque and expand the arterial wall, thereby restoring or improving the flow of blood to the local and distal tissues. Rotational atherectomy utilizes a similarly long and thin catheter, but with a rotational cutting tip at its distal end for cutting through the occluding material. Stenting utilizes a balloon tipped catheter to expand a small coil-spring-like scaffold at the site of the blockage to hold the blood vessel open.
While many patients are successfully relieved of their symptoms and pain with traditional interventional procedures, in a significant number of patients the blood vessels eventually restenose or reocclude within a relatively short period of time. As such, researchers have explored advanced interventional cardiology methods (e.g., catheter based drug delivery, radiation therapy, etc.) to delay or prohibit the process of restenosis. As summarized by Raoul Bonan, MD (“Local Drug Delivery for the Treatment of Thrombus and Restenosis, IAGS Proceedings, The Journal of Invasive Cardiology, 8:399-408, October 1996), the cardiology community has recently begun to augment standard catheter-based treatment techniques with devices that provide local delivery of medications to the treated site. This localized administration of drugs has shown promise for counteracting clotting, reducing inflammatory responses, and blocking proliferative responses.
Several devices are reported to be under evaluation for site specific drug delivery, such as the so-called “Channel Balloon” catheter of Boston Scientific (Natick, Mass.), the “Infiltrator” device of InterVentional Technologies (San Diego, Calif.), the “InfusaSleeve” device of LocalMed Inc. (Sunnyvale, Calif.), the “Dispatch” catheter of SciMed/Boston Scientific (Natick, Mass.), and an ultrasound enhanced catheter of EKOS (Bothell Wash.). The “Channel Balloon” catheter is an over-the-wire catheter with separated ports for balloon inflation and drug infusion. The “Infiltrator” device utilizes nipples in a balloon to force a drug into vessel wall.
U.S. Pat. No. 5,279,565 (Klein et al.) discloses a device for infusing a treatment site with a medicinal agent. The device has a flexible body and deflectable support frames that are deployed radially against the intended treatment site. The InfusaSleeve device of LocalMed, Inc. slides over existing balloons to position drug delivery ports against the artery wall. The Dispatch is an over the wire catheter with separate ports for drug infusion and balloon inflation.
U.S. Pat. No. 5,527,292 (Adams et al.) describes an intravascular device having an elongated flexible tube sized for insertion into a coronary vessel beyond a distal end of a guide catheter. In certain applications, the intravascular device is used as a drug (or other fluid) delivery device or as an aspiration device. In other applications, the intravascular device is used as a guiding means for placement of an angioplasty device, such as a guide wire or a balloon catheter. EKOS (Bothell, Wash.) has developed a site-specific catheter that uses ultrasound energy to enhance the performance of a thrombolytic drug. The ultrasound energy transports the drug molecules into the strands of fibrin bundles to dissolve clots more effectively than drugs alone. Several other drug delivery catheters have been described.
Balloon-tipped catheters, appropriate for drug delivery procedures, are also described in U.S. Pat. No. 5,087,244 (Wolinsky et al.). In particular, this patent describes a catheter having a balloon near its distal end is expanded with a medication that then flows through minute holes in the balloon surface at a low flow rate. The catheter pressurizes the medication so that it can be perfused at a controlled low flow rate to penetrate into the wall of the localized tissue.
U.S. Pat. No. 5,021,044 (Sharkawy) describes an intravascular treatment apparatus having a plurality of holes on the outer surface of the catheter body through which a drug may be delivered to a site within a vessel.
U.S. Pat. No. 5,112,305 (Barath et al.) describes a catheter for delivery of therapeutic chemical agents to an interior wall of a vessel, the catheter having a balloon near its distal end with tubular extensions projecting from its outer surface. The catheter is pressurized with a drug, which causes the balloon to expand. The drug then flows throughout the tubular extension into the vessel wall.
U.S. Pat. No. 4,406,656 (Hattler et al.) describes a collapsible multi-lumen venous catheter that can be used for drug injection.
U.S. Pat. No. 5,498,238 (Shapland et al.) discloses a method of simultaneous angioplasty and drug delivery to a localized portion of coronary or peripheral arteries or any other type of body passage that has a stricture. The drug delivery device is first positioned in a body passageway. The device is expanded in order to dilate the passage while simultaneously causing a selected drug to be transported across a drug transport wall of the device for direct contact with the passageway wall.
U.S. Pat. No. 5,415,637 (Khosravi) describes an intravascular catheter that is capable of delivering a drug, that is in the form of an already mixed solution or in the form of pellets, both intraluminally and endoluminally to an artery.
United States Letters Patent No. (Spears) describes a method for treating a lesion in an artery by bonding a bioprotective material to the arterial wall with thermal energy to provide localized drug delivery. The device can use drugs that are trapped within microspheres that can be thermally bonded to tissues.
U.S. Pat. No. 4,994,033 (Shockey et al.) describes an intravascular treatment apparatus having a pair of expansion members concentrically arranged near its distal end wherein a drug is delivered to the outer expansion member. The expansion member expands against the vessel wall forcing the drug through minute holes in the outer member to bathe the vessel wall.
U.S. Pat. No. 5,456,667 (Ham et al.) describes an intravascular catheter with an expandable region formed of a tubular material at the distal end of the catheter body in a one-piece configuration and is radially expanded and contracted by means of a control wire. The interior of the expandable region is in fluid communication with a lumen in the catheter body to allow the delivery of a fluid to the artery via openings in the surface of the expandable region. The catheter is particularly adapted to hold open an artery after a vascular procedure such as a balloon angioplasty, and if desired to introduce a therapeutic drug or other fluid to the site of the vascular procedure.
The assignee of this present invention is also the assignee of previously described catheter-based devices for the local delivery of drugs into the arterial system. See for example, U.S. Pat. No. 4,589,412 (Kensey) and U.S. Pat. No. 4,631,052 (Kensey) disclose atherectomy catheters that utilize a cutting tip that is driven by the application of fluid pressure. As described, the catheters can be used to deliver drugs, oxygen, nitrates, calcium channel blockers or contrast media through the catheter tip into the arterial lumen.
U.S. Pat. No. 4,747,406 (Nash) and U.S. Pat. No. 4,686,982 (Nash), which are assigned to the same assignee as this invention, describe recanalization catheters with a high speed working end that is driven by a flexible drive shaft mounted within a bearing. The specification describes the use of fluid to cool and lubricate the catheter, as well as reduce the incidence of snagging as a result of the positive pressure applied to the artery wall. The fluid can include nitrates, drugs, or contrast media.
U.S. Pat. Nos. 4,664,112 (Kensey), 4,679,558 (Kensey et al.), and 4,700,705 (Kensey), assigned to the same assignee as this invention, describe small diameter catheter devices with a high-speed working head used for dilating lumens and stopping arterial or other lumen spasm. The specifications describe the use of fluids to cool and lubricate the catheter. The fluid can carry contrast media or drugs. The catheters may be useful for opening restrictions in lumens by bombarding the restriction with propelled fluids at high pressure which may force the liquid into the lumen walls by increasing the local dynamic or hydrostatic pressure induced by the injected liquid or the moving working head.
U.S. Pat. No. 4,790,813 (Kensey), also assigned to the same assignee as this invention, describes an atherectomy catheter that utilizes a cutting tip that is driven by the application of fluid pressure. As described, that catheter has the potential for the delivery of drugs, oxygen, nitrates, calcium channel blockers or contrast media through the catheter tip into the arterial lumen.
U.S. Pat. No. 4,795,438 (Kensey et al.), also assigned to the same assignee as this invention, describes a flexible small diameter catheter for effecting the formation of a restriction in a vessel. The patent teaches of a rotary catheter that is used to deliver fluid, particles, sclerosing liquid, micron-sized particles, and adhesive agents. In one aspect of the invention, the particles are embedded into the tissue contiguous with the working head of the catheter. The embedded particles cause the tissue to change, e.g. form scar tissue, whereupon a restriction is formed. Another aspect of the invention describes the use of abrasive particles to sclerose or abrade tissue.
U.S. Pat. Nos. 4,749,376 (Kensey et al.), 5,042,984 (Kensey et al.), and 4,747,821 (Kensey et al.), all assigned to the same assignee of this invention, describe drive-wire driven rotary catheters for opening an arterial restriction. The devices utilize the rotation of a working head to cause fluid to be thrown radially outward from the working head to impact the artery wall.
In general, these previous devices are suited to deliver drugs and other therapeutic agents locally to the immediate lumen (e.g., artery) wall to address restenosis. However, they do not address the problem of treating other heart tissues (e.g., myocardium) located beyond the arterial wall.
It has been shown that some patients can receive significant benefits from recently developed medical treatments. Some of these treatments are applied to other tissues of the heart (e.g. the myocardium). In addition, although the non-surgical interventional cardiology procedures are much less costly and less traumatic to the patient than traditional coronary bypass surgery, there are a number of patients for which these procedures are not suitable. For certain types of patients the presence of extremely diffuse stenotic lesions and total occlusion in tortuous vessels prohibits them from being candidates for traditional cardiac surgery. For these patients, direct myocardial revascularization has been performed by inducing the creation of new channels, other than the coronary arteries themselves, which are designed to supply oxygenated blood and remove waste products from the heart tissue (e.g. myocardium). Myocardial revascularization is a technique that was conceived to supplement the blood supply delivered to the heart by providing the ischemic inner surface of the heart, known as the endocardium, with direct access to the blood within the ventricular chamber. Typically the endocardium receives its nutrient blood supply entirely from the coronary arteries that branch through the heart wall from the outer surface known as the epicardium.
Needle acupuncture approaches to direct myocardial revascularization have been made and were based upon the premise that the heart of reptiles achieve myocardial perfusion via small channels between the left ventricle and the coronary arterial tree as described by Sen et al. in their article entitled “Transmyocardial Acupuncture: A New Approach To Myocardial Revascularization” in the Journal of Thoracic and Cardiovascular Surgery, 50:181-187, August, 1965. In that article it was reported that researchers attempted to duplicate the reptilian anatomy to provide for better perfusion in human myocardium by perforating portions of the ventricular myocardium with 1.2 mm diameter needles in 20 locations per square centimeter. It has been shown that the perfusion channels formed by mechanical methods such as acupuncture generally close within two or three months due to fibrosis and scaring. Pifarre et al. evaluated the feasibility of direct myocardial revascularization from the left ventricle through artificially created channels. Their results are described in an article entitled “Myocardial Revascularization by Transmyocardial Acupuncture, A Physiologic Impossibility” in the Journal of Thoracic and Cardiovascular Surgery, 58:424-431, September, 1969. Pifarre et al. concluded that results were not encouraging. As a result, these types of mechanical approaches were abandoned in favor of other methods to effect the transmyocardial revascularization (TMR).
Similar revascularization techniques have involved the use of polyethylene tubes, endocardial incisions, and the creation of perforated or bored channels with various types of needles, and needle acupuncture. For example, T-shaped tubes have been implanted in the muscle, with the leg of the T-tube extending into the ventricular cavity as reported by Massimo et al. in an article entitled “Myocardial Revascularization by A New Method of Carrying Blood Directly From the Left Ventricular Cavity into the Coronary Circulation” appearing in J. Thorac. Surg., 34:257-264, August, 1957. In an article entitled “Experimental Method For Producing A Collateral Circulation To The Heart Directly From The Left Ventricle” by Goldman et al. in the Journal of Thoracic and Cardiovascular Surgery, 31:364-374, March 1965, several experimental methods for myocardial revascularization are described. One method involved the implantation of excised perforated carotid arteries into the left ventricular wall. Goldman et al. also examined the use of implanted perforated polyethylene tubing in a similar fashion.
U.S. Pat. No. 5,591,159 (Taheri) describes a device for effecting myocardial perfusion that utilizes slit needles to perforate the myocardium. The device uses a trans-femoral approach to position the device into the left ventricle of the patient. A plunger is activated to cause the needles to enter the myocardium several times. Perforation of the myocardium may be effected by means of a laser beam transmitted through the lumen of the needle or high velocity drill.
U.S. Pat. No. 5,655,548 (Nelson et al.) describes a method for perfusing the myocardium using a conduit disposed between the left ventricle and the coronary sinus. In one method, an opening is formed between the left ventricle and the coronary sinus, and the coronary ostium is partially occluded using a stent that prevents the pressure in the coronary sinus from exceeding a predetermined value. Blood ejected from the left ventricle enters the coronary sinus during cardiac systole. The apparatus limits the peak pressure in the coronary sinus to minimize edema of the venous system. The system utilizes retroperfusion via the coronary sinus of the venous system.
U.S. Pat. No. 5,755,682 (Knudson et al.) describes a device that establishes a channel leading directly from a chamber of a heart to a coronary artery. In one described method, a channel is created that extends through the deep coronary arterial wall through underlying cardiac musculature into the underlying chamber of the heart by using a scalpel, electro-surgical cutting blade, laser, or by radio-frequency ablation. A device is placed inside the channel to conduct blood from the heart chamber into the coronary artery.
Previous researchers had explored long term retroperfusion via the coronary sinus but found that its leads to edema of the cardiac veins which are incapable of sustaining long-term pressures above about 60 mm Hg. The procedure basically places a stent-like plug in the left ventricle so that blood flows into the coronary sinus and then into the myocardium via the venous system using retroperfusion, not into the myocardium directly. In the aforementioned Nelson et al. patent there is disclosed the use of a cutting instrument, such as a cannulated needle, a rotating blade, or medical laser to provide the required opening for the conduit. It is believed that when implanted in the heart, the plug and stent will result in long-term retrograde perfusion of the myocardium using the cardiac venous system and will cause a redistribution of the flow within the venous system so that a greater fraction of the deoxygenated blood will exit through the lymphatic stem and the Thebesian veins (any of the minute veins of the heart wall that drain directly into the cavity of the heart). The inventors also describe the use of a conduit that takes the place of the coronary sinus.
Researchers have also evaluated the used of lasers to create channels in the myocardium. U.S. Pat. No. 4,658,817 (Hardy) describes a surgical carbon dioxide laser with a hollow needle mounted on the forward end of the hand-piece. The needle is used to perforate a portion of the tissue, for instance the epicardium, to provide the laser beam direct access to distal tissue of the endocardium for lasering and vaporization. The device does not vaporize the tissue of the outer wall instead it separates the tissue which recoils to its native position after the needle's removal. This technique eliminates surface bleeding and the need for suturing the epicardium as is done with other techniques. The device includes a port that allows the needle to be cleaned via an injection of saline.
In U.S. Pat. No. 5,607,421 (Jeevanandam) discloses that laser channels remain open because carbonization associated with the laser energy inhibits lymphocyte, macrophage, and fibroblast migration. Thus, in contrast to channels created by needle acupuncture, laser channels heal more slowly and with less scar formation, which allows endothelialization and long term patency.
An article entitled “New Concepts in Revascularization of Myocardium” (by Mirhoseini et al. in Ann. Thor. Surg., 45:415-420, April 1988) discusses the work of investigators exploring several different approaches fordirect revascularization of ischemic myocardium. One revascularization technique utilizes “myoepexy”, which consists of roughening of the myocardial surface to enhance capillarization. Another technique, known as “omentopexy” (the operation of suturing the omentum to another organ), consists of sewing the omentum over the heart to provide a new blood supply. Another approach involves implanting the left internal mammary artery directly into heart muscle so that blood flowing through the side branches of the artery will perfuse the muscle.
It has been reported by Moosdorf et al. in their article entitled “Transmyocardial Laser Revascularization—Morphologic Pathophysiologic And Historical Principles Of Indirect Revascularization Of The Heart Muscle” in Z Kardiol, 86(3): 147-164, March, 1997 that the transmyocardial laser revascularization results in a relevant reduction of clinical symptoms such as angina and an increase of exercise capacity in approximately two thirds of the patients treated. Objective data of enhanced myocardial perfusion as assessed by positron emission tomography, thallium scans, and stress echocardiography has also been presented in other studies. Some researchers have found that TMR channels created by CO2 lasers are surrounded by a zone of necrosis with an extent of about 500 microns. In heart patients who died in the early postoperative period (1 to 7 days) almost all channels were closed by fibrin clots, erythrocytes, and macrophages. At 150 days post procedure, they observed a string of cicatricial tissue (scar tissue resulting from the formation and contraction of fibrous tissue in a flesh wound) admixed with a polymorphous blood-filled capillary network and small veins, which very rarely had continuous links to the left ventricular cavity. At the 2-week post procedure point a granular tissue with high macrophage and monocyte activity was observable. See for example, the article by Krabatsch et al. entitled “Histological Findings After Transmyocardial Laser Revascularization” appearing in J. Card. Surg. 11:326-331, 1996, and the article by Gassier et al. entitled “Transmyocardial Laser Revascularization. Historical Features In Human Nonresponder Myocardium” appearing in Circulation, 95(2): 371-375, Jan. 21, 1997.
PLC MEDICAL's (Franklin, Mass.) Heart Laser and Eclipse's (Sunnyvale, Calif.) TMR 2000 laser revascularization system's have recently been clinically tested and neither device has shown significant survival benefit between laser-based transmyocardial revascularization and medical management. However, in general the use of the devices did result in a two-class reduction in angina symptoms in the months following the procedure. Recent data was reported with respect to functional improvement, long-term survival, and angina relief after three years in 70 patients suffering from refractory angina yet not amenable to conventional revascularization. The patients were treated with PLC's CO2 Heart Laser. After the revascularization procedure with the Heart Laser, the angina class reduction seen at the first year persisted for at least three years with an accompanying increase in exercise tolerance. A significant increase in long-term mortality was not observed, however.
To date, studies have shown that no matterwhich laser, CO2 or Holmium are used, the clinical results following a laser-based transmyocardial revascularization procedure were almost identical: patients had an increase in exercise tolerance, a two-class reduction in angina symptoms, and no significant alteration in left ventricular ejection. BAXTER, J&J, CARDIODYNE and BARD/CORMEDICA are other companies that are also exploring laser-based TMR systems.
In co-pending U.S. patent application Ser. No. 08/958,788, filed on Oct. 29, 1999, entitled Transmyocardial Revascularization System, which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there is disclosed a system making use of mechanically created punctures to provide the same benefits as laser-created channels by initiating a healing response and effecting denervation in the myocardium. In particular, that system makes use of implants within the myocardial tissue to perpetuate a foreign body or healing response. That application additionally discloses the use of pharmaceuticals, growth factors and genetic material to provide the heart with an initial and perpetuating stimulus for healing itself.
More recently, other researchers have had related ideas Pelletier et al. examined myocardial channels created by lasers and the resulting injury that leads to an angiogenic response mediated by a number of growth factors. This work is described by Pelletier in “Angiogenesis and Growth Factor Expression in a Model of Transmyocardial Revascularization” (Annals of Thoracic Surgery, 66:12-18, 1998). With similar thoughts in mind, other companies are also investigating non-laser alternatives for myocardial revascularization. ANGIOTRAX (Sunnyvale, Calif.) is investigating a percutaneous device and flexible tip surgical handpiece for mechanically creating channels. BOSTON SCIENTIFIC (Natick, Mass.) is working with ARTHROCARE on the development of a radio-frequency (RF) system for percutaneous TMR. The device creates holes in the myocardium with needle electrodes that deliver RF energy at 450 kHz. The device utilizes a catheter that has been designed by SciMed. RADIUS MEDICAL (Maynard, Mass.) is exploring a percutaneous RF devices that utilizes a hollow guidewire, 0.021 or 0.035 inches in diameter that utilizes 13 kHz, that is passed through a 6 French diagnostic catheter. Contrast media is injected through the hollow wire to help position the device tip against the endocardial tissue. RADIUS believes that the hollow wire can be used to infuse proteins or genetic material into the myocardium. U.S. Pat. No. 5,810,836 (Hussein et al.) describes a stent for insertion into a heart wall for transmyocardial revascularization. The device generates needle-made, or drilled, channels in the heart wall. A stent is implanted in each channel to maintain the patency of the channel. In European Patent Application No. 97107784.7, assigned to United States Surgical of Norwalk, Conn., a coring device is described for removing tissue during a biopsy or transmyocardial procedures. The coring member is rotatable and linearly advanceable at coordinated predetermined rates to core body tissue. The tissue can be cauterized during the coring procedure. European Patent Application number 98201480.5 and PCT International application number PCT/US98/08819 of C. R. BARD in Murray Hill, N.J. describes a “TMR stent and delivery system.” That system includes a device which pierces the myocardial tissue and a stent which is implanted to permit the flow of blood from the left ventricle directly into the tissue for direct revascularization. Patent Cooperation Treaty (PTC) international application number PCT/US97/03523 of Energy Life Systems of Costa Mesa, Calif. describes a similar system. German patent number DE 296 19 029 U1 (Kletke) describes a needle for myocardial penetration. A needle is used to create a series of puncture canals. The canals are protected by the placement of continuous length of a resorbable suture, which is looped into each puncture.
In addition, researchers are exploring the percutaneous and direct surgical injection of growth factors and genetic material. Mack et al. describes experiments to improve myocardial perfusion in an article entitled “Biologic Bypass with the Use of Adenovirus-Medicated Gene Transfer of the Complementary Deoxyribonucleic Acid for Vascular Endothelial Growth Factor 121 Improves Myocardial Perfusion and Function in the lschemic Porcine Heart” in The Journal of Thoracic and Cardiovascular Surgery 115:168-177, January 1998. Sanborn et al. described the potential injection of angiogenic proteins and genes directly into the heart via the endocardium with a percutaneous fluoroscopically guided system in an abstract entitled “Percutaneous Endocardial Gene Therapy: In Vivo Gene Transfer and Expression” in the Journal of the American College of Cardiology 33:262A, February 1999. Uchida et al. described growth factor injections in “Angiogenic Therapy of Acute Myocardial Infarction by Intrapericardial Injection of Basic Fibroblast Growth Factor and Heparin Sulfate: An Experimental Study” American Heart Journal 130:1182-1188, December 1995. Uchida utilized a catheter system for percutaneous transluminal administration of drugs through the right atrium into the pericardial cavity with a 23 gauge 4 mm long needle. U.S. Pat. No. 5,244,460 (Unger et al.) describes a method for inserting a catheter into a coronary artery and for infusing multiple coronary drug injections, containing blood vessel growth promoting peptides (i.e. fibroblast growth factor), through an infusion port into the catheter over a period of time.
In summary, there are a number of potential mechanisms which individually or in combination may be responsible for the improvements seen in patients subjected to the previously described myocardial revascularization techniques including: (1) new blood flow through the created channels, (2) angiogenesis (stimulation of the creation of new blood vessels), (3) cardiac denervation, (4) the placebo effect, (5) ablation of ischemic myocardium, and (6) formation of collateral circulation.
Currently it is believed that cardiac denervation and angiogenesis are the primary causes for post procedure angina relief and improved perfusion respectively. The injury damages nerves thereby minimizing the pain sensation and stimulates angiogenesis. While the aforementioned techniques and methods for revascularizing the myocardium offer some promise they never the less suffer from one disadvantage or another. As a first example, the lasers are very expensive to purchase. The aforementioned U.S. patent application Ser. No. 08/958,788, filed on Oct. 29, 1997 is directed to the same or similar medical benefits achieved by use of non-laser devices, such as those disclosed and claimed therein. As a second example, the design of the interventional cardiology catheter-based drug delivery systems appear unable to delivery drugs to tissues located beyond the arterial walls. Significant benefit could be gained by the delivery of agents (e.g. foreign body particles, drugs, growth factors, genetic material, etc.) into heart tissues beyond the arterial wall. Those devices that have considered direct injection of drugs or genetic material into the myocardium simply deposit the material within a channel that is typically created by a needle. As the myocardium dynamically contracts, deposits of materials in these channels will likely migrate unless stabilized with a mechanical or chemical anchor of some sort. It is the intent of this invention to overcome these and other shortcomings of the prior art.